External Occipital Protuberance

What is External Occipital Protuberance?

The external occipital protuberance is a projection of the outer edge of the occipital squama. It is a normal part of the occipital bone, and is also called the "inion".

It is referred to as Protuberantia occipitalis externa in Latin and as Protubérance occipitale externe in French.

External Occipital Protuberance Location

It is located at about the central area of the squama, more or less in the center of the occipital bone. It is palpated easily as the projection over the skull's posterior surface. There is a weak crust, known as the external occipital crest and which offers attachment for the nuchal ligament, located under this projection that passes in an inferior manner to the foramen magnum's back surface.

External Occipital Protuberance Function

It offers attachment for the trapezius muscle's medial fibers. A section of the trapezius muscle is attached to the external occipital protuberance bump. This is the area where the neck meets with the head. The skull in this area is thicker and offers more protection.

External Occipital Protuberance Pain

Some people suffer from tenderness or pain on the external occipital protuberance or just under it. When the ligaments, muscles or tendons attached to the region get irritated, patients may suffer fom tightness, tenderness and pain at the base of the skull. This can lead to painful or difficult movement of the neck and head. The discomfort may also radiate down to the upper back or shoulder region or up to the head.

What is Prominent External Occipital Protuberance?

The prominent external occipital protuberance is a problem often revealed in X-rays and CT scans of the skull. It can be diagnosed by the appearing of a thin bony spur, and the projection make the head rotate in a ventrodorsal view.

External Occipital Protuberance Pictures

Look at the following external occipital protuberance images and diagrams to know about its overall appearance and how it looks like.